A Study On The Diagnostic Methods Of SARS Pathogen

To investigate the diagnostic value and the clinic significance of detecting the specific antibody and the SARS-cov gene in the samples of SARS patients. Serological methods (the Indirect ELISA and the Double antigen sandwich ELISA) to detect the specific antibody in the serum of SARS patients were compared. The relation between the results of detecting the specific antibodies in the serum of SARS and the severity of the symptoms of SARS patients, and the relation between the positive detection rate of the SARS-associated coronavirus and the severity of clinic symptoms, the course and the levels of specific antibody were investigated. The levels of the specific antibody in the serum of SARS patients in varied period, in different severity of symptoms, the healthy and feverous patients without SARS were detected by the Indirect ELISA and the Double antigen sandwich method. The S ARS-cov RNA in the sputum of these groups' were detected by nested RT-PCR. It was turn out that during 6-57 days of hospitalization, the SARS-cov gene in the sputum of 56 SARS patients were detected by nested RT-PCR, 34 of 56 cases are positive, the specific antibodies in 32 of 56 cases are positive by the Indirect ELISA. 20 cases of the healthy and 15 cases of the general feverous patients are all negative by two pathogen diagnostic methods, during 6-13days of hospitalization, the positive rate of SARS-cov RNA in the sputum of SARS by the nested RT-PCR(92.3%) is markedly higher than that of the specific antibodies in the serum of the SARS patients by the Indirect ELISA(7.7%); during >35days of hospitalization, the positive rate of SARS-cov RNA in the sputum of SARS by the nested RT-PCR(36.8%) is markedly lower than that of the specific antibodies in the serum of the SARS patients by the Indirect ELISA(94.7%)(P<0.01). The maximal positive detection rate of the specific antibody in the serum of SARS patients is 73.6% by the Double antigen sandwich method, whereas the maximal positive detection rate ofthe specific antibody in the serum of SARS patients is 57.5% by the Indirect ELISA. Furthermore, the positive detection rates of the specific antibody in the serum of SARS patients in varied period by the Double antigen sandwich method are higher than that by the Indirect ELISA. The IgG levels of the severe-symptom group is 2.9times than that of the light-symptom group and the IgM levels of the severe-symptom group is 1.7 times than that of the light-symptom group by the Indirect ELISA. the levels of the specific antibody of the severe-symptom group is 2.6 times than that of the light-symptom group by the Double antigen sandwich method. These results showed obviously that the levels of the specific antibody of the severe-symptom group is higher than that of the light-symptom group by two methods, the positive rate of the IgG of the severe-symptom group is 58.2% more than that of the light-symptom group and the positive rate of the IgG of the severe-symptom group is 22.1% more than that of the light-symptom group by the Indirect ELISA; the positive rate of the specific antibody of the severe-symptom group is 53.9% more than that of the light-symptom group by the Double antigen sandwich method, the sensitivity of the SARS-associated coronavirus RNA in the sputum of SARS patients detected by nested RT-PCR is 60.0% in total, the positive rate of the 6-10 days group is up to 100%, which is higher than that of the 11-25 days group, and the positive rate of the 11-25 days group is higher than that of the >25 days group(P<0.01); the positive rate of the light-symptom group is higher than that of the severe-symptom group (P<0.05); the positive rate of the negative specific antibody group by the nested RT-PCR is higher than that of the positive specific antibody group (P<0.05). It concluded that the early SARS patents could be diagnosed by detecting the SARS-cov gene in the sputum of SARS patients and it is of practical significance for diagnosing and curing the SARS patients and excluding the probable cases early. It is of limited sense for the early di...